Variable resistance device



July 27 1926. 1,593,658

L. L. JONES VARIABLE RESISTANCE DEVICE F ig ed Sept. 8, 1924 Tia. 1.

INVENTOR Lesfer L James BY I) I ATTORNEYS PATENT OFFICE.

LESTER L. JONES, OF ORADELL, NEW JERSEY.

VARIABLE RESISTANCE DEVICE.

Application filed September 8, 1924. Serial No. 736,507.

This invention relates to resistance devices, and more particularly tovariable or adjustable high resistance units.

In the art of radio communication, adjustable high resistance devicesare commonly employed for a number of purposes such as for adjustableinterstage amplifier resistor couplers for variable grid leakresistances, for audio frequency shuntresistances, for B battery voltagecontrol resistances and for audio frequency volume control rheostats.\Vhere resistances of values higher than that which can be economicallyobtained with wire'wound resistors are desired, it is common in the artto employ a high resistance element made up of a base having a graphitedor inked surface: and the adjustment or variation of resistance withsuch elements is obtained by moving a contact element such as a rheostatblade over and in contacting engagement with the graphited or inkedsurface of the resistance element.

The use and operation of this known type of variable high resistanceunit are. however, attended with a number of disadvantages. prime amongwhich are the absence of effective and sufiicient electrical contactbetween the rheostat blade and the high resistance surface, the presenceof microphonic contacts which result in introducing distortions when theresistance is used for example as a volume control rheostat, the changein resistivity of the resistance element and the mutilation and ultimatede struction of the high resistance element due to mechanical abrasionof the same result ing from the repeated movement of the rheostat bladeover the high resistance surface.

A prime desideratum of my present invention comprehends the provision ofvariable high resistance devices in which these disadvantages attendantand incident to the use of known high resistance devices areefi'ectively eliminated. and which possess the advantages characteristicof low resistance wire wound units such as efficient. stable andnon-microphonic contacts during the adjustment of the movable contactelement, maintenance of the integrity or identity of the resistance unitand its resistivity regardless of movement of the rheostat blade, andthe possibility of obtaining gradual and progressive predeterminedchanges or variations in resistance upon adjustment of the movablecontact element.

To the accomplishment of the foregoing and such other objects as willhereinafter appear, my invention consists in the elements and theirrelation one to the other, as hereinafter particularly described andsought to be defined in the claims; reference being had to theaccompanyin r drawings which show the preferred embodiments of myinvention. and in which:

Fig. 1 is a side elevational view of a preferred embodiment of theinvention with parts shown in section. v

Fig. 2 is a view thereof taken in crosssection on the line 22, Fig. 1.

Fig. 3 is a perspective view thereof show ing the parts detached, and

Fig. i is a fragmentary view of a modified form of the invention showingthe parts in detached relation.

.To accomplish the aforementioned objects, the invention in one of itsgeneric aspects comprises the interposition between the high resistanceelement and the adjustable contact of a wire wound element having itswindings conductively disconnected from one another and conductivelyconnected to the high resistance element, the adjustable contact beingmovable over and making contact with the windings of the wire woundelement. the construction being such that the movable contact is alwayshad between metal and metal. and the movement of the adjustable contactproduces progressive variations of resistance in the high resistanceelement.

Referring now more in detail to the drawings, the resistance unitof myinvention accordingly comprises generically a high resistance element a,a movable contact element such as the rheostat blade b, and a wire woundelement generally designated as c interposed between the high resistanceelement a and the movable blade 6, the said blade having contact withthe windings of the wire wound element. and the said windings beingconductively connected to the high resistance element a.

In the preferred embodiment of the invention, the resistance device isof the circular or arcuate type. the said resistance device comprising abase 10 made of an insulating material, the said base being providedwith an arcuate channel 11 on one side thereof, in which channel thehigh resistance element a and the wire wound element 0 are seated, thesaid base being provided with a central bore 12 through which isinserted a spindle or shaft 13, which spindle fixedly carries themovable blade I) at one end thereof and the control handle 14 at theother end thereof, the blade I) being held fixed to the shaft by meansof a securing nut 15 threadedly received by the threaded portion 16 ofthe spindle 12. The base 10 is also provided with a pair of bindingposts 17 and 18, the binding, post 17 being connected to the terminallead of the wire wound element 0, as will be described more in detailhereinafter. and the binding post 18 being conductively connected to thecontrol shaft 13 by means of a resilient connecting element 18. The highresistance element a desirably comprises a flexible base such as paper,fiber or the like having a graphited or inked surface, as clearly shownin Fig. 3 of the drawings, flexibility and pliability of the highresistance element being desirable so as to permit the readymanipulation of the resistance element and its insertion into thechannel 11 against the wall 11 thereof, and to permit the windings ofthe wire wound "element 0 to be pressed into intimate contact with thesurface of the high resistance element when the parts are assembled toobtain an effective and non-microphonic conductive connection ,betweenthe windings of the wire wound element and the high resistance surface.

The wire wound element 0', for economy and convenience of manufacture,comprises a flexible core 19 made of fiber or the like, about which iswound a coil or helix of the desired length, the said coil having itswindings severed or cut along one wall thereof after the windingoperation, producing contiguously arranged wire elements or windings 20which are conductivel disconnected from one another as will be fiillyapparent from a consideration of Figs. -1 to 3 of the drawings, each ofthe windings 20 comprising in effect a discontinuous loop having itssevered ends, along points in a wall 19 of the flexible core 19.Preferably a portion 21 of-the coil or helix is left uncut, the terminallead 22 of this portion being connected to the binding post 17.

In assembling the high resistance element and the wire wound element,the wire wound element is bent into arcuate form and inserted in thechannel of the wire wound core 19 is located in the bottom of thechannel, after which a flexible arcuate shaped wedge member 23 is forcedinto position between the wall 11 of the channel and the wire woundelement 0, the wire wound element being by this means securely locatedin the channel with the windings thereof pressed into intimate contactwith the surface of the high resistance liable commercial 11 so that thewall 19.

element a, the contiguous windings embedding themselves firmly in theresistance element to produce a long line contact between each windingand the high resistance ele ment, as is constructionally shown in Figs.11) and 2 of the drawings, and as is depicted y sistance strip a showndrawings.

In 'the preferred form of the invention as described, the highresistance element a is not incorporated as part of the core 19 of thewire wound element 0 but is made of a separate unit or element, themaking of the resistance element as a separate unit be ing preferred byreason of the numerous advantages ofliered thereby. It is requisite thatthe resistance path be formed on a base suitable therefor, and ithas-been found that the fibre strip or core (the core 19) on which thewire is wound is unsuitable for this purpose for a number of reasons.For example, it is not practical to form the resistance path after theflexible strip or core is curled for insertion into the molded base andif it be formed before the core or strip of the wire wound element iscurled, the resistance surface if incorporated as part of the core 19will be damaged by bending of the fibre strip because the fibre strip isfrom to inch wide and tends to compress'on its inner side and stretch onits outer side and so break the continuity of the resistance film. Ifthe resistance element is formed on a separate strip a such as paper orthin fibre suitable for the reception of a re sistance coating, thesedisadvantages are obviated. Therefore for purposes of economicalmanufacture and to produce a reresistance unit, I have found that theresistance film should be on a strip or element separate and distinctfrom the strip or core on which the contacting wires are wound. Wherethe resistance strip is made not only independent of the core 19 butseparate from the wire wound element as in the embodiment of the inveninFig. 3 of the tion illustrated herein, the manufacturer is enabled,moreover, to keep in stock standard contacting or wire wound elementsfor resistance strips of various sizes, since only the resistance stripelements need vary, the stock required by the manufacturer being thusconsiderably reduced. By making the resistance element separable fromthecore or separable from the wire wound element, I am enabled tofacilitate the assembling of the parts and to produce a unit whic 15efficient and durable in use.

lVith the employment of the principles of my invention, I am enabled toconstruct resistances having eirtremely wide ranges of resistivities,one form of such resistance be ing diagrammatically shown in Fig. 4 ofthe drawings,

in which the high resistance the relatively dense lines in the highreelement 1), comprises a flexible strip having regions ofdifierent.resistivities, the region 6 thereof being a very highresistance section made up of an inked surface, the region I)" thereofbeing of a comparatively lower resistance made up of a graphitedsurface, and the region 11 thereof being left untreated, this highresistance element b cooperating with the wire wound element 0 having anuncut section 24 cooperating with the clear or untreated section b ofthe high resistance element, the remaining windings of the wire woundelement 0 being cut and cooperating with the carbonized and inkedsections 19 and b of the high resistance element. The variation overeach region of the high resistance element and through the transitionpoints may be made continuous and gradual by overlapping the.

sections and tapering the high resistance surfaces, as is clearlydepicted in Fig. 4 of the drawings.

The manner of making. assembling and using the high resistance device ofmy invention will in the main be fully apparent from the above detaileddescription thereof. It will be further apparent that with theconstruction described, the high resistance unit has its filamentaryresistance threads connected in parallel at short intervals by the crossresistance wires of the wire wound element, this contributing to thecomplete elimination of microphonic contacts. It will be furtherapparent that by having the movable contact engaging the windings of thewire wound element, the integrity or identity of the high resistanceunit is maintained in service, the resistivity characteristics thereofbeing uninterfered with, and the mechanical abrasion and mutilation ofthe resistance unit incident to prior devices being entirely eliminated.It will furthermore be seen that in a construction embodying theprinciples of the invention, gradual and progressive predeterminedchanges or variations in the resistivity of the units may be obtained,as in low resistance wire wound units. A further important advantage ofthe invention resides in the fact that the resistance units may bemanufactured economically, the

comparative cheapness in cost of the inkimpregnated or graphited paperstrip and the wire wound element and the simplicity of manufacturing andassembling steps being factors in producing an eflicient high resistancedevice at low cost.

\Vhile I have shown the principles of the invention embodied in thepreferred form. it will be apparent that numerous changes inconstruction and arran ement of parts may be made without materiallydeparting from the essence of the invention. Thus it will be evidentthat the contiguously arranged wire elements interposed between themovable rheostat blade and the high resistance element need not be ofthe wire wound type, and it will be further evident that the highresistance element need not be made separate and independent of the wirewound element and arranged externally thereto, and that various otherchanges and arrangements of the parts may be produced without departingfrom the spirit of the invention, defined in the following claims.

I claim:

1. A high resistance device comprising a wire wound element including acore and windings thereon conductively disconnected from one another,and a separable high resistance element pressed into intimate conductiveengagement with the windings of the wire wound element.

2. A high resistance device comprising a high resistance "elementsurfaced with a resistance material, a wire wound element including acore independent of the resistance element and having windings thereonconductively disconnected from one another and conductively contactingwith the said resistance element, and means for pressing the windings ofsaid wire wound element into intimate contact with the surface of theresistance element.

3. A high resistance device comprising a wire wound element including aflexible core and windings thereon severed for conductivelydisconnecting the windings from one another and a flexible highresistance element separate from said core pressed into intimateconductive contact with an exposed side of the windings of the wirewound element.

4. A variable high resistance device comprising a wire wound elementincluding a core and windings thereon conductively disconnected from oneanother, a separable high resistance element pressed into intima'teconductive engagement with the windings of the wire wound element, andan adjustable contact element movable over and making contact with thewindings of the wire wound element,

5; A variable high resistance device comprising a wire wound elementincluding a flexible core and windings thereon severed for conductivelydisconnecting the windings from one another, a flexible high resistanceelement separate from said core pressed into intimate conductive contactwith a side of the windings of the wire wound element and an adjustablecontact element movable over and making contact with the windings of thewire wound element.

6. A variable high resistance device comprising an insulating base, anarcuate channel therein, a separable and flexlble high resistanceelementarranged agalnst a wall of said channel, and an arcuate wirewound element in said channel. having windings conductively disconnectedfrom one another a separable and flexible high resistance elementarranged against a wall of said channel, an arcuate wire wound elementin said channel having windings conductively disconnected from oneanother and pressed into "intimate contact with said high resistanceelement, and means for pressing the wire wound element into intimatecontact with the high resistance element.

8. A variable high resistance device comprising an insulating base, anarcuate channel therein, a flexible high resistance element arrangedagainst a wall of said channel, an arcuate wire wound element in saidchannel having windings conductively disconnected from one another and awedge forced between another wall of said channel and said wire woundelement and pressing the windings thereof into intimate contact withsaid high resistance element.

9. A variable resistance device comprising a high resistance elementhaving regions of different resistivities, and a wire wound clement,including a core, independent of the resistance element and havingcontiguously arranged windings thereon conductively disconnected fromone another and in conductive engagement with the diflerent regions ofsaid resistance element.

10. A variable high resistance device comprising an insulating base, anarcuate channel therein, a flexible high resistance element havingregions of difierent resistivities arranged against a wall of saidchannel, and an arcuate wire wound element in said channel having aportion of its windings cut for conductively disconnectin the same fromone another, said windings ing pressed into intimate contact with thedifi'erent regions of said high resistance element and a rotatablecontact element movable over and making contact with the windings of thewire wound element.

11. A high resistance device comprisin a wire wound element including acore an windings thereon conductively disconnected from one another, ana separate high resistance element independent of the wire wound elementand arranged externally to and pressed into intimate conductiveengagement with the windings of the wire wound element.

12. A high resistance device comprising a wire wound element including aflexible core and windings thereon conductively disconnected from oneanother, and a separate high resistance element composed of a flexiblebase surfaced with a resistance material independent of the wire woundelement and arranged externally to and pressed into intimate conductiveengagement with the wind ings'of the wire wound element.

Signed at New York city, in the county of New York and State of NewYork, this 6th day of September, A. D. 1924.

LESTER L.. JONES.

